Frame Dating: the easier you make it for folk to help you, the more likely they are to try.
The easiest way to date a Holdsworth, Claud or Grubb is to start with the frame number. This can give a very good indication of when the frameset was made and sometimes much more. Knowing the year made narrows the field enormously when trying to ID the model. See frame numbering chart and frame numbering system chart below.
Common Holdsworth frame number locations shown below.
Occasionally number move slightly from these locations and may have letters to signify frame builder particularly older models and shop builds.
Most pre-war Holdsworth’s have the frame number on the seat lug up to four digits long. Early frames also have this number repeat on the back of the fork crown, later this moved to the fork steerer tube.
Post WW2 numbers are generally under the BB using a five digit system but early Post-war with four digits numbers can still be found on sea lug. Initially centrally on the BB, a lot of early 1950’s models are stamped on the rear dropout, later in the 50’s the number moved to around the end of the BB and then finally high up on the drive side in the 60/70’s. This last position is also used for the later 6 digit system that came later. The frame number was repeated along the fork steerer tube in all cases. Throughout this time the change overs are not clear cut and exceptions also occur likely due to the frame builds preference and style.
There are two exceptions to the 5D system. First is in the early 1960’s when Holdsworth used a four digit system. This did not last long and soon went back to resuming the 5D system. This typically didn’t use leading zeros and can be confused with any early number from other systems, you have to look at frame style to confirm decade.
The second is the early 1970’s when a 4D system was used. This seems to be predominantly for frames built under license by other manufacturers and contract builds. It also seems to be used on early 70’s Holdsworth Shop builds making identifying these frames’ origins very difficult. Again it did not last long, but possibly longer than the 4D system in the 60’s.
Holdsworth Shop Numbers
First two digits for the year; typically ~200 frames each year but 1969, 74 & 75 numbers seem to have beed used across the folloing year too. Exact location and style does change due to the frame builder.
Starting in 1974 and from 1975 this system was used on Roy Thame frames until 1980, after that he used a plain number system untill Marlboro took over.
The frame number was repeated along the fork steerer tube in all cases.
Holdsworth Six Digit system
The various systems used up to 1976 are now replaced in this one style with a leading zero and located high up on the drive side of the bottom bracket (BB). On early frames some of the other leading zeros are dropped giving four or five digit numbers, but always one leading zero. The frame number was repeated along the fork steerer tube in all cases. There are only a few exceptions to this location such as with under BB double cable tunnels.
This system was also included any frames built under license by other manufacturers and contract builds most notably DBS’s Migliore, a Holdsworth Pro clone, and Hardings. The Holdsworth Shop never used this sytem as their bikes were badged Roy Thame during this period.
Marlboro Holdsworth & CB Frame Numbers
These are typically on the BB and have no discernible pattern to them. The could include letters, be in two parts and longer than 6 digits. these were also used on Roy Thame frames from ~1984. The frame number should be repeated on the fork steerer tube.
Falcon Holdsworth & CB Frame
Numbers seem to be stick on labels at the base of the seat tube. Other numbers are stapped on the BB including a batch number. There for it is not clear which number is repeated on the fork steerer tube.
Pre 1957 Claud Butlers
These frames can easily be dated to the exact month from the frame number alone.
1930/40’s numbers are 7 or 8 digits with the first 3/4 for the date and the last 4 for the frame sequence number. The decade has to be determined by frame features/style.
1950’s CB Numbers, typically two parts above each other without letters. The system started with date code above sequence number. During 1952/53 the order got mixed, by 1954 it was generally reversed. 1958 was different again the numbers were in one line 1930/40’s style initially across the BB but mainly around the edge suggesting early Holdsworth numbers.
Holdsworth Claud Butlers Numbers
Post 1958 numbers, similar 5 digit number to Holdsworth starting in ~1958 then re-started in 1967 at 50000 to avoid confusion with Holdsworth frames.
Freddie Grubb frame numbers
These numbers are typically up to five digits with no date coding.
FH Grubb & FHG numbers were commonly seen on the head lugs and fork crown but can also be seen under the BB too. Holdsworth Freddie Grubb only used BB and dropout locations
Unfortunately the number is usually coated with enamel. On some frames, where the paint is thin and the digits well stamped the frame number will be easily read. If the enamel is thick however, it often causes a digit mis-read, especially when digits are badly stamped. On rare occasions a digit can be completely filled with enamel and rendered invisible. Fortunately, the same frame number is also stamped on the fork steerer tube, irrespective of year made. The number is much easier to read here, because it is not painted over and protected inside the head-tube, every digit will be clear. Pre 1957 Clauds may also have a builder code stamped with the steerer tube number, this is not stamped on the frame.
To date or ID your model you should ideally remove the forks and take a clear pic of all steerer tube numbers, also get a pic of the frame number from the frame if you can. Matching numbers should confirm each digit of the frame number and that the forks are original to that frame. They usually are, but this is useful because then the fork crown, lamp boss braze-on (or lack of one), dropouts etc may be used with confidence as model ID features. Frame numbers can be looked up in the table below and verified by online forums; post the pic(s), clearly showing the frameset serial number, to a web-based discussion forum (see classic links on home page). Some of the enthusiasts should be able to date it for you. Note that it is not uncommon to see CB’s with two frame numbers usually an original CB number and also a Holdsworth number. This usually means the frame has been back to Holdsworth for a refurbishment and in some cases more than once. The forks should have the same new number, but if the new one is the only one then the forks have been replaced. This is typically seen on CB frames but could conceivably happen with Holdsworth and Grubb frames, but the renumbering of these frames is very seldom seen if at all.
If you want to ID a frame look through the catalogues on this site for the relevant year paying attention to items in the description like lugs, fork crown, frame angles etc. also the decals used, finish & head badge, but remember to note if the frame has been restored. It also worth considering which features on a frame could have been added or removed during its life and which are permanent. The same is true of the frame number style and location, it is also worth noting if the number has been altered in any way. See, for example, the two photo galleries on the L’International page; one is unrestored with original paint and matching frame numbers, the other is a restored frameset. Features such as geometry and lug design can not be changed without considerable effort so it is probable that these ‘permanent’ features were there from the start and are therefore key to its ID. Both frames are the same in this respect.
Most braze-ons were optional on a shop builds and options were also available for factory models too, all of these items could be tampered with later in life. Note the differences in the two L’International‘s; mudgaurd tabs have been removed, cable stops & gear lever boss have been added to the frameset. In addtion the fork lugs do not match and the dropouts are different. Most of these features can be easily changed, even the dropouts and forks can be replaced. Working out what is original, changed and what was optional is difficult to know. In this case the unrestored example looks closer to the catalouge and style of the day, but has a simpler fork crown dispite matching frame number on its steerer. Although listed as new in 1939 both of these frames would have been built during or just after WW2 at a time when production was ramping up again. Also pre-war stock would have been being used up and the line up getting modernised; all of this could explaine the differences.
If the catalogues do not clarify what model a frame is it is also worth posting close-up pics of key ID features online.
Holdsworth, CB & Grubb Frame Numbers
Frame numbers found so far can be found in This Database. This also includes charts of potential number progressions for each numbering style used by Holdsworth, CB & Grubb summarised below.
Frame Numbering
